Slight simplification to the query optimizer logic associated with IN (SELECT).
FossilOrigin-Name: 2c55c3c2950cafdc256ab540f60dc4609b9c354b
diff --git a/src/expr.c b/src/expr.c
index 22ca21de..3672d02 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -1568,24 +1568,22 @@
}
/*
-** Return true if we are able to the IN operator optimization on a
-** query of the form
-**
-** x IN (SELECT ...)
-**
-** Where the SELECT... clause is as specified by the parameter to this
-** routine.
-**
-** The Select object passed in has already been preprocessed and no
-** errors have been found.
+** pX is the RHS of an IN operator. If pX is a SELECT statement
+** that can be simplified to a direct table access, then return
+** a pointer to the SELECT statement. If pX is not a SELECT statement,
+** or if the SELECT statement needs to be manifested into a transient
+** table, then return NULL.
*/
#ifndef SQLITE_OMIT_SUBQUERY
-static int isCandidateForInOpt(Select *p){
+static Select *isCandidateForInOpt(Expr *pX){
+ Select *p;
SrcList *pSrc;
ExprList *pEList;
+ Expr *pRes;
Table *pTab;
- Expr *pRes; /* Result expression */
- if( p==0 ) return 0; /* right-hand side of IN is SELECT */
+ if( !ExprHasProperty(pX, EP_xIsSelect) ) return 0; /* Not a subquery */
+ if( ExprHasProperty(pX, EP_VarSelect) ) return 0; /* Correlated subq */
+ p = pX->x.pSelect;
if( p->pPrior ) return 0; /* Not a compound SELECT */
if( p->selFlags & (SF_Distinct|SF_Aggregate) ){
testcase( (p->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct );
@@ -1601,15 +1599,15 @@
if( pSrc->nSrc!=1 ) return 0; /* Single term in FROM clause */
if( pSrc->a[0].pSelect ) return 0; /* FROM is not a subquery or view */
pTab = pSrc->a[0].pTab;
- if( NEVER(pTab==0) ) return 0;
+ assert( pTab!=0 );
assert( pTab->pSelect==0 ); /* FROM clause is not a view */
if( IsVirtual(pTab) ) return 0; /* FROM clause not a virtual table */
pEList = p->pEList;
if( pEList->nExpr!=1 ) return 0; /* One column in the result set */
pRes = pEList->a[0].pExpr;
if( pRes->op!=TK_COLUMN ) return 0; /* Result is a column */
- if( pRes->iTable!=pSrc->a[0].iCursor ) return 0; /* Not a correlated subq */
- return 1;
+ assert( pRes->iTable==pSrc->a[0].iCursor ); /* Not a correlated subquery */
+ return p;
}
#endif /* SQLITE_OMIT_SUBQUERY */
@@ -1741,15 +1739,13 @@
** satisfy the query. This is preferable to generating a new
** ephemeral table.
*/
- p = (ExprHasProperty(pX, EP_xIsSelect) ? pX->x.pSelect : 0);
- if( pParse->nErr==0 && isCandidateForInOpt(p) ){
+ if( pParse->nErr==0 && (p = isCandidateForInOpt(pX))!=0 ){
sqlite3 *db = pParse->db; /* Database connection */
Table *pTab; /* Table <table>. */
Expr *pExpr; /* Expression <column> */
i16 iCol; /* Index of column <column> */
i16 iDb; /* Database idx for pTab */
- assert( p ); /* Because of isCandidateForInOpt(p) */
assert( p->pEList!=0 ); /* Because of isCandidateForInOpt(p) */
assert( p->pEList->a[0].pExpr!=0 ); /* Because of isCandidateForInOpt(p) */
assert( p->pSrc!=0 ); /* Because of isCandidateForInOpt(p) */